Inelastic Neutron Scattering (INS) Study of Low Frequency Vibrations and Hydrogen Bonding of (E)-Benzil Monoxime

(E)-benzil monoxime (or (E)-monoxime of 1,2 diphenyloetandion), which is the subject of this paper, belongs to the family of bioactive organic substances. Many of them have been investigated for many years by inelastic, incoherent neutron scattering spectroscopy (IINS) but the investigation of (E)-benzil monoxime is absent from literature. Therefore (E)-benzil monoxime has been investigated using infrared, and IINS spectroscopy. Dimers of (E)-benzil monoxime were considered using B3LYP functional (connection of Becke and Lee–Yang–Parr functionals) combined with the 6-311++G(d,p) basis set method of quantum chemistry in order to improve the results obtained for a single molecule. In (E)-benzil monoxime, extra bands corresponding primarily to hydrogen bond vibrations (γ bending out of plane of hydrogen bond at 312.3, 372, 470.5, 578.3, 703.5, 748.7, 780.4 cm –1, σ stretching of hydrogen bond bridge at 124.3, 140.9, 176.5, 190.1, 223.6, 259.1, 290.5, 501.8, 623.5 cm –1, δ bending in plane of hydrogen bond at 1102.4, 1371,1452,1535, 1630.6 cm –1, λ bending of hydrogen bond bridge at ca. 40 cm –1, ν stretching band OH at 3397 cm –1) have been identified. Some of them could be discovered only by using IINS method and this is the main result of this work. Additionally we'd like to compare the structure of the compound and the structure of oximes previously investigated by us . Taking into account the structure and IINS results for three oximes investigated by us, we can estimate the difference of hydrogen bond power in those three oximes. Hence the power of hydrogen bond in the (E)-benzil monoxime seems to be the smallest in the group of the three compounds: (E)-benzil monoxime, (E)-2-hydroxyimino-2-cyanoacetic acid ethyl ester (2-oxime), acid K salt of 2-oxime.

Resonance Raman and absorption infrared with density functional theory studies of Fe(III)/Fe(II) and Ni(II) complexes of modified 21-oxaporphyrins

This work presents a complete vibrational analysis of iron [ Fe (II) and Fe (III)] and nickel [ Ni (II)] complexes with 5,10,15,20-tetraphenyl-21-oxaporphyrin [OTPPH] and 5,20-bis(p-tolyl)-10,15-diphenyl-21-oxaporphyrin [ODTDPPH]. In these porphyrins, a furan ring replaces one of the pyrrole rings. The six-coordinate (OTPP) FeIIICl2 and (ODTDPP) FeIIICl2 as well as the five-coordinate (OTPP) FeIICl and (OTPP) NiIICl complexes were investigated using experimental and theoretical methods. The experimental part of this work involved Fourier-transform absorption infrared (FT-IR), resonance Raman (RR), and electron absorption (UV-vis) measurements for all of the investigated complexes. In the theoretical section, optimized geometries and vibrational frequencies for model compounds are provided. The theoretical calculations were performed at the B3LYP level with the LANL2DZ basis set. Good agreement was achieved between the experimental and theoretical vibrational spectra. In addition, charge distributions (GAPT) and geometrical aromaticity indices (Bird's I5 and HOMA) were calculated and discussed.

Chiral Recognition in Diaziridine Clusters and the Problem of Racemization Waves

Theoretical calculations (B3LYP/6-31+G**) of chiral clusters of diaziridines have been carried out. Five configurations of chiral and nonchiral clusters with up to eight monomers have been considered. The proton transfer within the neutral and protonated clusters has been studied as a possible source of racemization waves. The optical rotatory power (ORP) has been calculated for the neutral and protonated homochiral clusters. The results show that the clusters with alternated chiral molecules are the preferred ones and that the proton transfer proceeds with low energetic barriers in the protonated systems. The ORP results are very dependent on the shape of the clusters and the neutral or protonated state of them.

Theoretical Study of Dihydrogen Bonds between (XH)2, X = Li, Na, BeH, and MgH, and Weak Hydrogen Bond Donors (HCN, HNC, and HCCH)

The dihydrogen-bonded (DHB) complexes formed by (XH)2, with X = Li, Na, BeH, and MgH, with one, two, and four protonic molecules (HCN, HNC, and HCCH) have been studied. These complexes have been compared to those of the XH monomers with the same hydrogen bond donor molecules. The energetic results have been rationalized based on the electrostatic potential of the isolated hydridic systems. The electron density properties have been analyzed within the AIM methodology, both at the bond critical points and the integrated values at the atomic basins. Exponential relationships between several properties calculated at the bond critical points (rho,nabla2rho, lambdai, G, and V) and variation of integrated properties (energy, charge, and volume) vs the DHB distance have been obtained.

Effect of Dimerization and Racemization Processes on the Electron Density and the Optical Rotatory Power of Hydrogen Peroxide Derivatives

The variation of the electron density properties and optical rotatory power of the monomers and dimers of seven monosubstituted hydrogen peroxide derivatives, HOOX (X = CCH, CH(3), CF(3), t-Bu, CN, F, Cl), upon racemization has been studied using DFT (B3LYP/6-31+G) and MP2 (MP2/6-311+G) methods. The geometrical results have been rationalized on the basis of natural bond orbital (NBO) analysis. The atomic partition of the electron density properties within the atoms in molecules (AIM) methodology has allowed investigating the energy and charge redistribution in the different structures considered. The calculated optical rotatory power (ORP) of the dimers are, in general, twice of the values obtained for the monomers.

Enantioselective chromatography of alkyl derivatives of 5-ethyl-5-phenyl-2-thiobarbituric acid studied by semiempirical AM1 method

Complexation of alkyl derivatives of 5-ethyl-5-phenyl-2-thiobarbituric acid (2-thiophenobarbital) enantiomers by beta-cyclodextrin was investigated by the AM1 method. The inclusion complexes of beta-cyclodextrin with neutral and anionic forms of these enantiomers have been modeled and energetically optimized. The chiral discrimination of enantiomers was analyzed in terms of differences in the interaction energies. The calculated interaction energies between each enantiomer of the investigated 2-thiobarbiturates and beta-cyclodextrin confirm the ability of beta-cyclodextrin to act as a mobile phase additive in reversed-phase HPLC to separate enantiomers by liquid chromatography and rationalize their order of elution.